Ya!! what sonia says is the perfect answer to decide the size of data block.

For OLTP - the small transactions are more in nos as compared to large blocks requested by queries. and for DSS system - no of transactions are less but the queries requesting the large data are more.

It is recommended that if you have a VLDB and a HYBRID system , then you should keep two databases on for OLTP ( Small data block size ) which is used for small transactions and other for DSS (Large data block size ) which is only for large requests, i mean only for reports used for MIS or so.

Even the rest of the answers are correct.